Effects of driver sheet on magnetic pulse forming of AZ31 magnesium alloy sheets

Theoretical predictions of dynamic necking formability of ductile metallic sheets with evolving plastic anisotropy and tension-compression asymmetry

“…The tests were performed at different forming speeds, with the maximum strain rate attained in the experiments varying between 1200 s −1 and 3500 s −1 . As in the free-bulging tests of Xu et al [50,48], in which the samples were subjected to nearly equibiaxial stretching, the tensile formability of the AZ31 sheets in the electromagnetic experiments of Xu et al [49] was significantly greater than in conventional quasi-static tests, the increase in the major and minor limit strains being 112% and 96%, respectively. Electromagnetic free-bulging forming experiments on Ti-6Al-4V sheets of 1 mm thickness were performed by Li et al [27] using a driver plate made of AA5052-O with 2 mm thickness.…”

“…The higher increase in ductility for conical-die forming can be explained by the fact that in this case an additional deformation occurs during the impact of the blank against the die [18]. Xu et al [50,48] carried out electromagnetic free-bulging forming experiments with AZ31 magnesium sheets of 1 mm thickness. The tests were performed with and without an aluminum driver sheet.…”

“…Shortly after, the same authors carried out electromagnetic forming experiments with AZ31 magnesium sheets subjected to uniaxial tension [49]. The thickness of the samples was 1 mm, as in the experiments of Xu et al [50,48]. The tests were performed at different forming speeds, with the maximum strain rate attained in the experiments varying between 1200 s −1 and 3500 s −1 .…”

“…Electromagnetic free-bulging forming experiments on Ti-6Al-4V sheets of 1 mm thickness were performed by Li et al [27] using a driver plate made of AA5052-O with 2 mm thickness. As in the formability tests performed by Xu et al [50,48] with AZ31 magnesium specimens, the driver plate was used in order to reach high forming velocities, up to 165 m/s, that otherwise would be difficult to attain due to the low conductivity of the titanium alloy. Postmortem analysis of the specimens showed that the major and minor limit strains were 0.093 and 0.028, respectively.…”

“…All these experimental results substantiate the pioneering claim of Balanethiram and Daehn [5] that the beneficial contribution of inertial forces to the formability of metals sheets is both large and general, as it affects most ductile metallic materials. On the other hand, the experimental evidence is that the quantitative effect of inertia on formability improvement depends on the strain state [26,50,48,49], and also on the mechanical behavior of the material, since the extent of the formability improvement is different for different metal sheets [18,42]. Nevertheless, as of today, it is not clear which features of the constitutive behavior of the material affect the most to the dynamic ductility of the metal sheets.…”